Due to technical and aesthetic reasons, trim parts are fixed to any kind of support parts of the vehicle by fixing means that are provided only on one surface of the trim part, for example the inner surface without leaving any marks on the other surface, i.e., the outer surface. The method known in the art comprises following steps for establishing a fixing connection between the trim part and the support part:                aligning the trim part and the supporting part such that the fixing means and the counter means can be engaged to each other, and        engaging the fixing means with the counter means by applying force to the outer surface of trim part.        
Since the fixing means do not leave any marks on the outer surface on which the force is applied, following problem arises. Upon assembly, the operator is facing the outer surface opposing the inner surface of the trim part. Since trim parts are often planar and relatively large, the fixing means are almost invisible to the operator. As a result, the operator does not know the exact position of the fixing means when applying force to the outer surface when engaging the fixing means to the counter means. Trim parts are often made of thin material. In many cases, cavities are formed between the trim parts and the support parts. When the operator is applying force to the outer surface of the trim part that is at distance from the fixing means, the trim part is prone to deformation which results in damage to the outer surface. This deformation of the trim part decreases the part quality and increases part rejections. The replacement of defect trim parts is time consuming and costly.
U.S. Pat. No. 5,117,549 discloses a method for fastening an interior trim part to a vehicle door by using adhesive beads and fasteners. However, the fasteners do not leave any marks on the outer surface and thus, the position of the fasteners is difficult to estimate when fastening the interior trim part to the vehicle door.
It is an object of the present invention to reduce the drawbacks of the previous methods. In particular, a method is presented that enables the estimation of the position of the fixing means when looking on the outer surface of the trim part upon assembly.